:root {
  --grow-time: 5s;
  --fade-time: 3s;
}

body {
  overflow: hidden;
  padding-top: 80px;
  text-align: center;
}

.controls {
  position: relative;
  z-index: 2;
}

.controls__label {
  display: block;
  font-family: Menlo;
  font-weight: bold;
  margin-bottom: 10px;
}

.controls__slider {
  width: 200px;
}

.circle {
  -webkit-animation: grow var(--grow-time) forwards, fade var(--fade-time) calc(var(--grow-time) - var(--fade-time)) forwards;
          animation: grow var(--grow-time) forwards, fade var(--fade-time) calc(var(--grow-time) - var(--fade-time)) forwards;
  background: #81ecec;
  border-radius: 100%;
  height: 2px;
  left: 20vw;
  position: absolute;
  top: 20vh;
  -webkit-transform: translateZ(0);
          transform: translateZ(0);
  width: 2px;
}

@-webkit-keyframes grow {
  0% {
    -webkit-transform: translateZ(0) scale(0);
            transform: translateZ(0) scale(0);
  }
  
  100% {
    -webkit-transform: translateZ(0) scale(100);
            transform: translateZ(0) scale(100);
  }
}

@keyframes grow {
  0% {
    -webkit-transform: translateZ(0) scale(0);
            transform: translateZ(0) scale(0);
  }
  
  100% {
    -webkit-transform: translateZ(0) scale(100);
            transform: translateZ(0) scale(100);
  }
}

@-webkit-keyframes fade {
  0% {
    opacity: 1;
  }
  
  100% {
    opacity: 0;
  }
}

@keyframes fade {
  0% {
    opacity: 1;
  }
  
  100% {
    opacity: 0;
  }
}